a push or pull acting on a body; vector quantities; measured in Newtons; 

point of application: where it makes contact

line of action: how you draw lever arms

weight (gravity)

Ground Reaction Force

Friction

Fluid Resistance

joint reaction force

muscle force

Intertia: object's resistance to a change in motion; measured by an object's mass (kg)

tries to resist acceleration

more mass=more inertia

Accerleration: F=ma

must have an unbalanced force to have accerleration

sum cannot equal zero if you're going to overcome accereleration

Reaction: for every active force, there is a second force that is equal in magnitude, yet opposite in direction

forces ALWAYS occur in pairs

what we feel is the force coming back to us (like when punching a wall)

mass moment of intertia: I=mk^2

centroid of where mass is; takes into consideration the shape of the axis, decreases k, less restance to spin, so will spin faster; 

moment of inertia, increase forgiveness of bat, club, etc

moment (M) or torque

rotational force

M=I(alpha)

for every appled moment, there is a second moment that is equal in magnitude, yet opposite in direction

edge of a cliff...when falling backwards, rotate arms that direction to push you back forward

rotart effect of a force; angular equivalent of force; vector; rotational and twisting actions;

AKA: moment of force or torque

true definition of what happens inside the body

governed by right hand screw rule; 

1. curl fingers in direction of rotation

2. direction the thumb point represents direction of vector

magnitude given in Nm

sign based on coordinate system

1. balance two or more forces

2. change the directin of an applied force

3. mechanical advantage for Speed/ROM

4. mechanical advantage for force production

FAR

products must equal each other to be at equilibrium

length of lever arms allows for mechanical advantage

longer RMA=speed/ROM

longer FMA=force production

only class that can accomplish all four fxns

Triceps press down (elbow extension)

Neck extension

ARF

FMA will always be longer than RMA

least common in body

major function: force production

calf raises

push ups

AFR

most common in body

insertion/tendon is where force is

muscles set up lever systems, not bones

seated knee extension

elbow flexion (biceps curl)

external surface that changes line of pull of a muscle

ex: patella-increases horizontal angle of pull

trochlea is involved-internal surface that changes line of pull of a muscle

ex: lateral malleolus: 3 peroneus-eversion; longus/brevis: plantar flexion; tertiary: dorsiflexion

ex: eye-anteror lateral position; oblique superior

second and fifth equally most common

joint structure itself causes a change in the line of pull

ex: knee-sartorius goes around knee to attach because of condyles

as muscle contracts, it changes angle of joint, which changes its own line of pull

ex: forearm-pronators, suppinators; pronator teres

no stationary axis

must be two muscles: deep and superficial

deep muscle shortens and increases cross-sectional are, which changes angle of pull of superifical muscle

ex: gastroc/soleus; biceps/brachialis